Streamer cable depth control



April 29, 1969 c. L. CHANCE STREAMER CABLE DEPTH CONTROL Sheet Filed Dec. 7, 1967 FIG wATE FLOW PIC-3.2.

INVENTOR. Calvin L. Chance BY WW ATTORNEY April 29, 1969 c. L. CHANCE STREAMER CABbE DEPTH CONTROL Sheet I Filed Dec. 7, 1967 e c a Y m u w Z Li m or m A V O C V. B

United States Patent Tex.

Filed Dec. 7, 1967, Ser. No. 688,909 Int. Cl. B63b 17/00; G01c 13/00 US. Cl. 114235 Claims ABSTRACT OF THE DISCLOSURE An automatic depth-control device for attachment to a seismic streamer cable of the type which is towed behind a survey vessel at a predetermined depth beneath the surface of the sea, the streamer cable itself being weighted to approximate neutral buoyancy in the water, and the depth-control device including a hydrostatic pressure system for continuously maintaining the desired depth by controlling the angle of tilt of a horizontal vane in a manner which in its broadest aspects has been disclosed in the prior art. The structure of the depth-control device is illustrated by an embodiment including a faired housing enclosing a frame and bearing assembly which is split longitudinally for easy attachment at any desired position along the streamer cable to rotatably secure the device to the cable in such a way as to permit the device to freely rotate about the cable to maintain itself always in upright position. The upper portion of the housing is filled with a floatation material which is sufficient to impart neutral buoyancy to the whole device, and is so placed as to provide a restorative moment about the bearing for maintaining the housing upright and the vane substantially horizontal.

The disclosure relates to improvements in streamer cable depth-control devices of the type having adjustable vane surfaces automatically tilted by depth-sensing means as the cable is towed along, a plurality of such devices generally being spaced along the cable as necessary to control its towing depth within desired tolerances.

It is a principal object of this invention to provide a small depth control device which is streamlined to provide quiet non-turbulent towing as viewed by the sonic transducers within the streamer cable, and depth control device which is self-righting to an extent sufiicient to keep the planing vanes substantially horizontally disposed.

It is another major object of this invention to provide a depth control device including in its combination of elements a rotatable bearing mount which provides stable attachment of the control device to the cable free of rotational binding thereon.

Another principal object of the invention is to provide in combination with a depth-control device a secure bearing mount, attachable anywhere along the cable, and quickly and easily applied to and removed from the cable. This quick-detachable feature is especially useful when the streamer cable is being deployed from a rolled-up and stored position to a use-position in the water. Ordinarily depth-control devices of the present type cannot be left on the cable when it is being coiled for storage aboard the towing vessel.

A further object of the invention is to provide a depthcontrol device in which the axis of tilt of the vane mounting substantially intersects the axis of the bearing mount so that no significant moment of rotation is imparted to the frame of the device by the vanes, which moment would tend to cause the control device to rotate from upright position about the cable-mount bearing.

Other objects and advantages of the invention will become apparent during the following discussion of the drawings, wherein:

3,440,992 Patented Apr. 29, 1969 FIG. 1 is a plan view of a device according to the invention, but showing the upper housing removed;

FIG. 2 is an elevation view of the device with the fairing housing broken away to show the interior structure;

FIG. 3 is a sectional view taken along lines 3-3 of FIG. 2; and

FIG. 4 is an exploded view of the mounting and operating mechanism of the device.

Referring now to the drawings, the streamer cable S is oil filled and weighted to give it neutral buoyancy in a manner well known per se. The cable S is provided with a rigid exterior bearing surface B by placing two semicylindrical sleeves 1a and 1b around it. These are held together on the cable by snap rings 2 located near opposite ends of the resulting composite sleeve, these snap rings compressing the resilient surface of the cable S to hold the bearing sleeve 1a-1b securely in place thereon. The snap rings 2 are preferably located in grooves 10 in the outer surfaces of the sleeve members 1a and 1b to prevent displacement of the snap rings longitudinally thereof.

The remaining structure of the depth control device is mounted upon a frame F comprising four longitudinal angle bars 3, 4, 5, and 6 which are attached to split bearing blocks 7a-7b, and 8a8b. The angle bars 3 and 4 and the angle bars 5 and 6, when laid together, provide abutting outwardly extending flanges 9 and 10 which are held together by quarter-turn fasteners 11 which serve the purpose of holding together the frame F including angles 3, 4, 5 and 6 and the bearing block halves 7a-7b and and 8a-8b. The bearing blocks 7 and 8, when thus held together as part of the frame F, provide internal bearing surfaces B which ride on the outer surfaces B of the sleeve members 1a and 111, this structure being clearly visible in the exploded view of FIG. 4.

Referring now to FIGS 2 and 4 the angle bar 5 carries a bearing support 12 on its under surface, and a stub shaft 13 extends through this hearing support and is attached by members 14 and 15 to the surface of a lift vane 16, the attachment being made at the center of the lift vane as shown in the drawings. A crank arm 17 is attached to the inner end of the shaft 13 and extends downwardly and connects near its lower end with a rod 19 which extends transversely across the frame F and connects with another crank arm 20, which controls the angle of the lift vane 21 on the other side of the depth control device, the lift vane 21 and its operating mechanism and support means being the same as those just described in connection with lift vane 16. The rod 19 which extends between the crank arms 17 and 20 is connected to a control rod 22 which in turn extends into a pressure tank 23 and connects to the rear end of a bellows 24 in such a way that the rod 22 is reciprocated back and forth with respect to the support plate 25, which mounts the front end of the tank 23, whenever the bellows changes length axially of the tank 23 to move the rod 19 in the direction of the arrow A. The pressure tank 23 has a duct 26 and a valve 27 communicating with the inside of the tank through which a predetermined amount of air pressure can be preloaded into the tank against the outer surfaces of the bellows 24. The inside of the bellows 24 is vented to the sea by a vent opening 28, FIG. 2, whereby the depth to which the assembly is lowered in the sea will determine the pressure inside the bellows 24 and thus determine the axial position of the rod 22, so as to rock the crank arms 17 and 20 back and forth in the direction of the arrow A and therby adjust the tilt of the lift vanes 16 and 21 in the directions indicated by the arrow T.

In order to reduce water flow turbulance about the depth control device to a bare minimum, the frame and operating mechanism thereof are enclosed within a'resystem reaches an equilibrium when the sea water pressure acting inside of the bellows 24 through the vent 28 is balanced by the air pressure preloaded into the tank 23 surrounding the bellows 24. If the whole unit is being towed too deeply in the sea, the pressure will be greater within the bellows 24 than outside of it, and the rod 22 will be pulled further forward into the tank 23, thereby displacing the lower ends of the crank arms 17 and 20 in a direction to tilt the vanes 16 and 21 upwardly to cause the entire assembly to rise against the flow of water W as the cable is towed through the sea. Conversely, if the whole assembly is being towed at too shallow a depth, the pressure entering the bellows 24 through the duct 28 will be lower than the preloaded pressure within the tank 23, and the bellows will contract and displace the rod 22 rearwardly of the device to tilt the crank arms 17 and 20 in a direction to deflect the vanes 16 and 21 downwardly, thereby causing the depth control device to plunge deeper into the sea. The preadjustment of the air pressure in the tank 23- will determine the point of equilibrium and therefore the towing depth of the device. It is to be understood that other fluids than air can be used Within the tank 23.

The fairing halves 30 and 31 of the depth control device can be opened up for installation or removal with respect to the streamer cable S by removing the band 32 and disassembling the fairing covers 30 and 31 from the frame F. The split bearing blocks 7 and 8 can be opened by release of the quarter-turn fasteners 11, thereby removing everything from the cable except the sleeve members la-lb and the snap rings 2. These latter can of course be removed by unsnapping the rings from the grooves 1c near the ends of the bearing sleeve members la and 1b.

As mentioned in the objects of this invention, floatation material 35 must be added to the inside of the upper fairing member 30 to cause the depth control device always to lie upright in the water. The quantity of this floatation material, such as styrene foam 35, should be suificient to provide the over-all depth control device with substantially neutral buoyancy when the tank 23 is charged with fluid pressure.

The novel features of the disclosure illustrated by the above described practical embodiment are claimed as follows:

1. In a depth-control device to be rotatably mounted upon a'streamer cable to maintain the latter'at a desired depth when towed under water, the device including means for maintaining the device in upright position about its longitudinal axis and including planing vane means extending from the device and including water-pressure responsive means connected to automatically control the tilt of the vane means to continuously restore the device and the cable toward the desired depth, the structure of the device comprising:

(a) a longitudinally-split cylindrical sleeve diametrically sized to snuggly surround the cable and long enough to underlie at least half the longitudinal length of the depth-control device;

(b) means to clamp the split sleeve tightly around the cable;

(c) paired upper and lower bearing block means respectively having semi-cylindrical inner bearing surfaces cooperative with the outer surfaces of the sleeve, and the paired block means being spaced apart to occupy positions near the opposite ends of the sleeve;

(d) upper and lower longitudinal frame members joining together, respectively, the upper block means and the lower block means, and said upper and lower frame members being coupled together when the respective block means are mated, and said block means and members comprising a frame which is substantially axially coextensive with said sleeve and is connected to support the vane means and the pressure responsive means; and

(e) means to confine the block means axially on said sleeve.

2. In a device as set forth in claim 1, said sleeve comprisng opposed semicylinders snuggly fitting the cable and having annular groves circumferentially disposed in their outer surfaces; and snap ring means occupying said grooves and holding said semicylinders together.

3. In a device as set forth in claim 2, said bearing block means surrounding the sleeve adjacent to said annular grooves, and said snap ring means confining the bearing block means to prevent axial displacement thereof from said sleeve.

4. In a device as set forth in claim 1, a faired housing having openings to pass the the housing being split into tosecure the shells together cable and the vane means, opposed shells; and means about the frame.

5. In a device as set forth in claim 4, floatation means placed and secured in upper portions of said housing when in upright position to provide a center of buoyancy located above the center of the cable.

TRYGVE M. BLIX, Primary Examiner. 

